U.S. patent application number 14/307704 was filed with the patent office on 2015-01-22 for speaker magnetic circuit.
This patent application is currently assigned to JVC Kenwood Corporation. The applicant listed for this patent is JVC Kenwood Corporation. Invention is credited to Hiroyuki KUMAKURA.
Application Number | 20150023545 14/307704 |
Document ID | / |
Family ID | 52343598 |
Filed Date | 2015-01-22 |
United States Patent
Application |
20150023545 |
Kind Code |
A1 |
KUMAKURA; Hiroyuki |
January 22, 2015 |
Speaker Magnetic Circuit
Abstract
A yoke includes a disk-like base end portion and a columnar
center pole protruding from a center portion of the base end
portion. An annular magnet is arranged on the base end portion. An
annular top plate is arranged on the magnet so that an inner
circumferential surface thereof is opposite to an outer
circumferential surface of the center pole. A non-magnetic ring
member is arranged on an inner circumferential surface side of the
magnet, the non-magnetic ring member having a same inner
circumferential diameter as an inner circumferential diameter of
the top plate.
Inventors: |
KUMAKURA; Hiroyuki;
(Yokohama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JVC Kenwood Corporation |
Yokohama-shi |
|
JP |
|
|
Assignee: |
JVC Kenwood Corporation
Yokohama-shi
JP
|
Family ID: |
52343598 |
Appl. No.: |
14/307704 |
Filed: |
June 18, 2014 |
Current U.S.
Class: |
381/412 |
Current CPC
Class: |
H04R 9/025 20130101;
H04R 1/00 20130101; H04R 9/022 20130101 |
Class at
Publication: |
381/412 |
International
Class: |
H04R 15/00 20060101
H04R015/00; H04R 3/00 20060101 H04R003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 19, 2013 |
JP |
2013150371 |
Mar 10, 2014 |
JP |
2014046071 |
Claims
1. A speaker magnetic circuit comprising: a yoke including a
disk-like base end portion and a columnar center pole protruding
from a center portion of the base end portion; an annular magnet
arranged on the base end portion; an annular top plate arranged on
the magnet so that an inner circumferential surface thereof is
opposite to an outer circumferential surface of the center pole;
and a non-magnetic ring member arranged on an inner circumferential
surface side of the magnet, the non-magnetic ring member having a
same inner circumferential diameter as an inner circumferential
diameter of the top plate.
2. The speaker magnetic circuit according to claim 1, further
comprising: a voice coil arranged in a magnetic gap formed between
the outer circumferential surface of the center pole and the inner
circumferential surface of the top plate, wherein an end portion of
the non-magnetic ring member, the end portion being located on the
base end portion side, is located more on the base end side than an
end portion of the voice coil, the end portion being located on the
base end portion side, when an audio signal is inputted to the
voice coil and the voice coil is located most on the base end
portion side.
3. The speaker magnetic circuit according to claim 2, wherein,
between the end portion of the non-magnetic ring member, the end
portion being located on the base end portion side, and the base
end portion, a gap larger than the magnetic gap is formed, the gap
being formed between the outer circumferential surface of the
center pole and an inner circumferential surface of the magnet.
4. The speaker magnetic circuit according to claim 1, wherein the
non-magnetic member is formed of metal containing aluminum.
5. The speaker magnetic circuit according to claim 1, wherein an
inner circumferential surface of the non-magnetic ring member is a
smooth surface free from irregularities.
6. The speaker magnetic circuit according to claim 1, wherein a
plurality of longitudinal grooves arrayed in a circumferential
direction is formed on an inner circumferential surface of the
non-magnetic ring member.
7. The speaker magnetic circuit according to claim 1, wherein a
plurality of dot-like recessed portions is formed on an inner
circumferential surface of the non-magnetic ring member.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority under 35U.S.C..sctn.119 from Japanese Patent Application
No. 2013-150371, filed on Jul. 19, 2013 and No. 2014-046071, filed
on Mar. 10, 2014, the entire contents of both of which are
incorporated herein by reference.
BACKGROUND
[0002] The present disclosure relates to a speaker magnetic
circuit.
[0003] As described in Japanese Patent Laid Open Publication No.
H08-9494 (Patent Literature 1), a magnetic circuit of a general
external magnetic-type speaker includes a top plate, a magnet, and
a yoke. From the center of the yoke, a center pole protrudes.
Between an inner circumferential surface of the top plate and an
outer circumferential surface of the center pole, a magnetic gap is
formed. In the magnetic gap, a voice coil wound around a voice coil
bobbin is arranged.
[0004] Japanese Patent Laid Open Publication No. 2009-124200
(Patent Literature 2) describes that, in order to enhance heat
radiation of the speaker, air from a diaphragm is guided to a cover
that covers the magnetic circuit, and the magnetic circuit is
cooled. Japanese Patent Laid-Open Publication No. 2006-60443
(Patent Literature 3) describes that a heat radiating member is
installed on the top plate to thereby cool down the top plate.
Japanese Patent Laid-Open Publication No. 2005-341475 (Patent
Literature 4) describes that heat radiating components are
installed on and under the top plate.
[0005] In accordance with such technologies described in Patent
Literatures 2 to 4, heat from the voice coil is drawn indirectly,
whereby the voice coil can be cooled down.
SUMMARY
[0006] In accordance with the above-described technologies, heat
from the voice coil at a portion that is located in the magnetic
gap formed between the top plate and the yoke can be drawn.
However, in the above-described technology, heat from the voice
coil at a portion that is not located in the magnetic gap cannot be
drawn, and heat from the whole of the voice coil cannot be
dissipated.
[0007] The inventor of the present disclosure has inspected a heat
failure of the speaker, and then it was found that the voice coil
at the portion that is not located in the magnetic gap frequently
causes a layer to short circuit. This indicates that the heat from
the voice coil at the portion that is not located in the magnetic
gap is not dissipated sufficiently.
[0008] It is an object of the embodiments to provide a speaker
magnetic circuit capable of effectively radiating the heat from the
voice coil and thereby enhancing heat resistance of the voice
coil.
[0009] An aspect of the embodiments provides a speaker magnetic
circuit comprising: a yoke including a disk-like base end portion
and a columnar center pole protruding from a center portion of the
base end portion; an annular magnet arranged on the base end
portion; an annular top plate arranged on the magnet so that an
inner circumferential surface thereof is opposite to an outer
circumferential surface of the center pole; and a non-magnetic ring
member arranged on an inner circumferential surface side of the
magnet, the non-magnetic ring member having a same inner
circumferential diameter as an inner circumferential diameter of
the top plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a cross-sectional view of a speaker magnetic
circuit of a first embodiment, showing a position of a voice coil
when the voice coil is turned to a non-energized state.
[0011] FIG. 2 is a cross-sectional view of the speaker magnetic
circuit of the first embodiment, showing a position of the voice
coil when the voice coil is turned to an energized state.
[0012] FIG. 3 is a perspective view showing a non-magnetic ring
member for use in the speaker magnetic circuit of the first
embodiment.
[0013] FIG. 4 is a cross-sectional view showing a speaker unit for
use in the speaker magnetic circuit of the first embodiment.
[0014] FIG. 5 is a perspective view showing a non-magnetic ring
member for use in a speaker magnetic circuit of a second
embodiment.
[0015] FIG. 6 is a perspective view showing a non-magnetic ring
member for use in a speaker magnetic circuit of a third
embodiment.
DETAILED DESCRIPTION
[0016] A description is made below in detail of the speaker
magnetic circuits of the first to third embodiments with reference
to the accompanying drawings. For the sake of convenience, a
vertical direction in the drawings is defined as a vertical
direction of the speaker magnetic circuits or speaker units.
First Embodiment
[0017] As shown in FIG. 1, a speaker magnetic circuit 1 includes a
yoke 2, a magnet 3, a top plate 4, and a non-magnetic ring member
5.
[0018] The yoke 2 includes: a base end portion 2a formed into a
disk shape; and a columnar center pole 2b protruding upward at a
center portion of an upper surface of the base end portion 2a. The
yoke 2 is composed of a magnetic body.
[0019] The magnet 3 is formed into a ring shape having a through
hole 3h having a radius obtained by adding a gap G to a radius of
the center pole 2b. The magnet 3 is arranged on the base end
portion 2a in a state where the center pole 2b penetrates the
through hole 3h. The magnet 3 is magnetized on the vertical
direction of FIG. 1.
[0020] The top plate 4 is formed into a ring shape having a through
hole 4h having a radius obtained by adding a magnetic gap MG
smaller than the gap G to the radius of the center pole 2b. The top
plate 4 is arranged on the magnet 3. The top plate 4 is composed of
a magnetic body.
[0021] The center pole 2b is inserted into the through hole 4h of
the top plate 4. An inner circumferential surface of the top plate
4 is opposite to an outer circumferential surface of the center
pole 2b.
[0022] The non-magnetic ring member 5 has the same inner
circumferential diameter as an inner circumferential diameter of
the top plate 4 (that is, a diameter of the through hole 4h). The
non-magnetic ring member 5 is arranged so as to be brought into
intimate contact with an inner circumferential surface of the
magnet 3 and a lower surface of the top plate 4.
[0023] A position of the inner circumferential surface of the
magnet 3 is located outward in a diameter direction more than a
position of the inner circumferential surface of the top plate 4 by
a thickness of the non-magnetic ring member 5. Hence, when the
non-magnetic ring member 5 is arranged on the inner circumferential
surface of the magnet 3, the position of the inner circumferential
surface of the top plate 4 and a position of the inner
circumferential surface of the non-magnetic ring member 5
substantially coincide with each other.
[0024] A corner portion 5e in which the inner circumferential
surface of the non-magnetic ring member 5 and a lower end surface
thereof intersect with each other is formed into a fillet with a
round and smooth curved surface.
[0025] FIG. 3 is a perspective view showing the non-magnetic ring
member 5 in the first embodiment. As shown in FIG. 3, the inner
circumferential surface of the non-magnetic ring member 5 in the
first embodiment is a uniform and smooth surface (surface free from
irregularities).
[0026] A speaker unit 6 using the speaker magnetic circuit 1 is
composed as shown in FIG. 4. A frame 7 formed into a substantially
truncated cone shape is fixedly attached onto an upper surface of
the top plate 4.
[0027] Onto a step portion 7a formed in a lower portion of the
frame 7, an outer circumferential portion of an annular damper 8 is
fixedly attached. Concentric corrugations are formed in the damper
8. A cylindrical voice coil bobbin 9 is fixedly attached onto an
inner circumferential portion of the damper 8.
[0028] A voice coil 10 is wound around an outer circumference of
the voice coil bobbin 9, which is located below a spot thereof onto
which the damper 8 is fixedly attached. The voice coil 10 is wound
around the outer circumference concerned in a predetermined range
from a lower end portion of the voice coil bobbin 9.
[0029] When the voice coil 10 is in a non-energized state, a lower
portion of the voice coil bobbin 9 is located in the magnetic gap
MG formed between the outer circumferential surface of the center
pole 2b and the inner circumferential surface of the top plate 4.
With regard to the voice coil 10, an upper portion thereof is not
located in the magnetic gap MG, and most of a lower portion thereof
is not located in the magnetic gap MG.
[0030] An inner circumferential portion of a diaphragm 11 expanded
upward in diameter is fixedly attached onto an upper portion of the
voice coil bobbin 9. An inner circumferential portion of an annular
edge 12 in which a cross-sectional shape is formed into a
semicircle is fixedly attached onto an outer circumferential
portion of the diaphragm 11. An outer circumferential portion of
the edge 12 is fixedly attached onto a step portion 7b formed in an
upper portion of the frame 7.
[0031] A dome-like cap 13 is fixedly attached onto a halfway
portion of the diaphragm 11 so as to close an upper opening of the
voice coil bobbin 9.
[0032] When an audio signal is inputted to the voice coil 10, and
the voice coil 10 is turned to an energized state, then by a
function of the magnetic circuit, the voice coil bobbin 9 and the
voice coil 10 move vertically in accordance with the audio signal.
In such a way, the diaphragm 11 vibrates in the vertical direction,
and the speaker unit 6 emits a sound.
[0033] FIG. 2 shows a state where the voice coil bobbin 9 is
located at a lowest position (base end portion 2a side) thereof at
a time of a maximum amplitude by the input of the audio signal to
the voice coil 10. A lower end of the non-magnetic ring member 5
(that is, an end portion thereof on the base end portion 2a side)
is located more downward than a lower end of the voice coil 10 when
the voice coil bobbin 9 is located at the lowest position.
[0034] In the state of FIG. 2, with regard to the voice coil 10,
the lower portion is not located in the magnetic gap MG, and the
upper portion is located in the magnetic gap MG.
[0035] The non-magnetic ring member 5 is formed, for example, of
metal containing aluminum as a main body. Specifically, the
non-magnetic ring member 5 is formed of a non-magnetic body such as
aluminum or an aluminum alloy, and does not affect a magnetic flux
density in the magnetic gap MG.
[0036] As described above, the corner portion 5e on the lower end
of the inner circumferential surface of the non-magnetic ring
member 5 is formed into the fillet, and accordingly, turbulence
owing to such a vertical motion of the voice coil bobbin 9 is less
likely to occur.
[0037] The gap G composed between the inner circumferential surface
of the magnet 3 on a lower portion of the non-magnetic ring member
5 and the center pole 2b is larger than the magnetic gap MG.
[0038] In general, when a moving speed of air in contact with an
object rises, then a heat transfer rate of the air is increased.
This is obvious since a heat transfer rate h defined in Expression
(1) is in a proportional relationship with a heat flux density
J.
h = Q A ( Tw - Ta ) = J Tw - Ta ( 1 ) ##EQU00001##
[0039] In Expression (1), Q is a heat movement (W), J is the heat
flux (W/m.sup.2), A is a heat transfer area (m.sup.2), Tw is a
temperature (K) of an object surface, and Ta is a temperature (K)
of a fluid, where Tw>Ta.
[0040] That is to say, when a moving speed of air in contact with
the voice coil 10 rises, then the heat transfer rate of the air is
increased. If the moving speed of the air in contact with the voice
coil 10 is raised, then the air can draw heat of the voice coil 10
efficiently.
[0041] In order to raise the moving speed of the air, a
cross-sectional area of a region where the voice coil 10 moves, the
cross-sectional area being taken along a direction perpendicular to
a moving direction thereof, only needs to be decreased.
[0042] As shown in FIG. 1 and FIG. 2, an inner diameter of the
magnet 3 is larger than an inner diameter of the top plate 4. The
gap G under the magnetic gap MG is larger than the magnetic gap MG.
In the first embodiment, the non-magnetic ring member 5 having the
same inner circumferential diameter as that of the top plate 4 is
arranged on the inner circumferential surface of the magnet 3, and
accordingly, the cross-sectional area of the region where the voice
coil 10 moves is constant. Hence, in accordance with the speaker
magnetic circuit 1 of the first embodiment, the moving speed of the
air can be raised in comparison with a case where the non-magnetic
ring member 5 is not present, and the heat of the voice coil 10 can
be drawn efficiently.
[0043] In the first embodiment, the lower end of the non-magnetic
ring member 5 does not abut against the base portion 2a of the yoke
2, and the gap G is formed in a vicinity of the base end portion
2a.
[0044] If the lower end of the non-magnetic ring member 5 abuts
against the base end portion 2a, a compression ratio of the air is
increased at a time when the voice coil 10 is lowered, and
accordingly, the voice coil 10 becomes difficult to move. By the
fact that the gap G is present in the vicinity of the base end
portion 2a, the voice coil 10 can be moved smoothly.
[0045] Moreover, in a case where a stroke of the voice coil 10 is
small since the audio signal is weak, a flow of the air disappears
in a lowermost portion of the gap G, and the heat is accumulated.
The gap G, which is larger than the magnetic gap MG, and is present
in the vicinity of the base end portion 2a, becomes an air chamber.
Hence, circulation of the air occurs, thus making it possible to
prevent the accumulation of heat.
[0046] In accordance with the speaker magnetic circuit 1 of the
first embodiment, the heat of the voice coil 10 is radiated
efficiently, thus making it possible to enhance heat resistance of
the voice coil 10.
Second Embodiment
[0047] Next, a description is made of the speaker magnetic circuit
of the second embodiment with reference to FIG. 5. Here, a
description is made of only a point in which the second embodiment
is different from the first embodiment, and a duplicate description
is omitted.
[0048] FIG. 5 is a perspective view of a non-magnetic ring member
52 in the second embodiment. The speaker magnetic circuit of the
second embodiment is a circuit in which the non-magnetic ring
member 5 in the speaker magnetic circuit 1 of the first embodiment
is replaced with the non-magnetic ring member 52.
[0049] As shown in FIG. 5, a plurality of longitudinal grooves 52a
arrayed in a circumferential direction is provided on an inner
circumferential surface of the non-magnetic ring member 52 in the
second embodiment. The longitudinal grooves 52a are extended in a
direction parallel to the moving direction of the voice coil 10. In
an example shown in FIG. 5, the plurality of longitudinal grooves
52a is arrayed at an equal interval in the circumferential
direction.
[0050] In such a way, while setting such a gap when the voice coil
10 is lowered at the maximum amplitude at the same gap as the
magnetic gap MG, a contact area of the air in the gap with the
non-magnetic ring member 52 can be increased. Hence, in accordance
with the second embodiment, the heat of the voice coil 10 can be
drawn efficiently.
[0051] In accordance with the speaker magnetic circuit of the
second embodiment, the heat of the voice coil 10 is radiated
effectively, thus making it possible to enhance the heat resistance
of the voice coil 10.
Third Embodiment
[0052] Next, a description is made of the speaker magnetic circuit
of the third embodiment with reference to FIG. 6. Here, a
description is made of only a point in which the third embodiment
is different from the first embodiment, and a duplicate description
is omitted.
[0053] FIG. 6 is a perspective view of the non-magnetic ring member
53 in the third embodiment. The speaker magnetic circuit of the
third embodiment is a circuit in which the non-magnetic ring member
5 in the speaker magnetic circuit 1 of the first embodiment is
replaced with the non-magnetic ring member 53.
[0054] As shown in FIG. 6, a plurality of dot-like recessed
portions 53a are formed on an inner circumferential surface of the
non-magnetic ring member 53 in the third embodiment. For example,
the recessed portions 53a have a hemispherical shape. In an example
shown in FIG. 6, the plurality of recessed portions 53a is arranged
uniformly on the inner circumferential surface.
[0055] In such a way, while setting such a gap when the voice coil
10 is lowered at the maximum amplitude at the same gap as the
magnetic gap MG in a similar way to the second embodiment, a
contact area of the air in the gap with the non-magnetic ring
member 53 can be increased. Hence, in accordance with the third
embodiment, the heat of the voice coil 10 can be drawn
efficiently.
[0056] In accordance with the speaker magnetic circuit of the third
embodiment, the heat of the voice coil 10 is radiated effectively,
thus making it possible to enhance the heat resistance of the voice
coil 10.
[0057] The present invention is not limited to the first to third
embodiments described above, and is changeable in various ways
within the scope without departing from the spirit of the present
invention.
* * * * *